'Bottom up' sensory representations are shaped by 'top down1 influences, such as behavioral state and attention. Mammalian olfaction has been a subject of intense interest since the discovery of its fundamental receptor units, but little is known about how receptor-based coding mechanisms interact with central feedback projections in the main olfactory bulb (MOB). The adrenergic locus coeruleus (LC) transmits information about arousal and attention. Norepinephrine (NE) plays a role in several olfactory learning behaviors and has known effects on MOB circuitry in vitro. This study will investigate how LC input shapes representations of individual identity carried by urine volatiles. Experiments will: 1) observe LC activity in awake mice during social olfactory interaction and learning 2.) test the specific lasting effects of LC activation on odor responses of MOB neurons and olfactory perception 3.) determine the cellular circuit mechanisms of this olfactory plasticity. These studies will provide a rare opportunity to examine the effects of arousal and attention on ethologically relevant perception. They are also generally relevant to mechanisms of cognitive flexibility and related pathologies such as attention deficit hyperactivity disorder. [unreadable] [unreadable] [unreadable]